1. Field of the Invention
This invention relates to a method for identifying hydrocarbon crude oil constituents and more particularly, to a method for identifying hydrocarbon crude oil by electron spin resonance signals.
It has been known for some time that most crude oils exhibit electron spin resonance so that the presence of these crude oils may be detected by measurements of the resonant absorption of energy from a radio frequency electromagnetic field encompassing a sample. With presently available laboratory apparatus, both qualitative and quantitative analysis may be made of samples through electron paramagnetic resonance measurements of absorption of radio frequency electromagnetic energy in magnetic fields. Simply stated, the energy absorbed in these analyses is absorbed at the frequency of precession of almost free electrons in the crude oil sample. The free radicals that exhibit the absorption of this radio frequency energy are characteristic of certain chemical structures and are peculiarly present in the chemical structures of crude oil. The free radicals exhibit the property of having a magnetic moment because of uncompensated electron spin; hence, they are paramagnetic.
Many other materials also exhibit electron spin resonance and, unfortunately, some of these many other materials may be found in their natural state in association with petroleum crude. While it may be possible to distinguish between the electron spin resonance signals of crude oil from the electron spin resonance signals of other materials, such distinguishing techniques are frequently elaborate laboratory procedures that must be performed with carefully controlled laboratory equipment. To avoid the confusion between electron spin resonance signals from crude oils and similar signals from other materials, it is therefore desirable to develop a simple technique which may be used to distinguish the two signal sources.
A further confusion as to the source of electron spin resonance signals can exist when making measurements within or along a well bore penetrating an earth formation because electron spin resonance signals may be produced from crude oils as well as from heavy hydrocarbon refined products. Electron spin resonance signals may be derived from the heavy ends of refined products such as residuum or possibly from some heavy gas oils, but will not be derived from diesel, gas, butane or other light ends. Such heavy refined products might exist along a well bore in the form of oil based drilling muds or from other hydrocarbons used in drilling fluids. It is therefore an additional desire to provide a method that will permit a distinction to be made between signals derived from crude hydrocarbons and signals derived from refined hydrocarbon products.
2. Prior Art
As so far as I am aware, no prior at exists for the technique that is herein disclosed. U.S. Pat. No. 3,060,371, J. Townsend et al, issued Oct. 23, 1962, For Geological Prospecting Process and Apparatus, discloses an early concept of the geological prospecting process wherein electron spin resonance signals from unpaired electrons in carbonaceous materials may be detected and used in the prospecting process. Later investigators have suggested the use of electron paramagnetic resonance signal measurements from crude oils as a means for identifying the presence of crude oil along subsurface earth formations. One such disclosure is found in U.S. application Ser. No. 745,959, of Robert R. Unterberger, filed July 1, 1958, For Electron Paramagnetic Resonance Well Logging, now abandoned, wherein a technique is described for measuring electron paramagnetic resonance signals along the bore of a well penetrating an earth formation. Other investigators have suggested the enhancement of electron paramagnetic signals by subjecting the unpaired electrons to additional radiation; however, such enhancement techniques require elaborate laboratory equipment and it is substantially impossible to perform these techniques within a well bore within an earth formation.
The object of the present invention is to provide a simple enhancement mechanism for improving the electron spin resonance signals derived from hydrocarbon crude oil and for distinguishing the electron spin resonance signals from crude oil from those signals which could be derived from most refined hydrocarbon products, coal or shale.
A further object of the present invention is a simple and inexpensive method for suppressing the electron spin resonance signals from crude petroleum.
Further objects and features of the present invention will be readily apparent to those skilled in the art from the appended drawings and specification describing the preferred techniques in accordance with the foregoing objects.